Provision of frames or borders around pigment flakes for covert security applications

Abstract

Opaque flakes, such as pigment or bright flakes used in paints and inks, have a selected shape and/or other indicia to provide a covert security feature to an object. Shaped opaque covert flakes are not readily detectable by causal observation, but in some embodiments are easily seen at 50× magnification. In manufacturing the flakes a sheet of embossed frames are provided having embossed symbols or indicia within. Upon removing a coating from the embossed sheet the coating material tends to break along frame lines or grooves and the resulting flakes are substantially uniform in size. In order to have the flakes break along frame lines or grooves more readily than along the embossing or grooves defining indicia within a frame, the frames are provided with a deeper groove than indicia grooves. As well a groove having a different shaped profile conducive to breakage can be used for the frame grooves whereas a groove having a profile less conducive to breakage can be used to form the indicia grooves. We have found that the flakes can be further protected from breakage by coating them in a protective coating. This coating may have other features which makes the logo more visible.

What is claimed is: 
     
       1. A plurality of pigment taggent flakes, each flake having
 a first surface; 
 an indicia defined by one or more regions having a second surface extending in a first direction with respect to the first surface to a maximum distance I d  from the first surface, and 
 a frame defined by one or more walls disposed at a periphery of the flake so as to at least partially surround the indicia, each wall extending in the first direction to a distance of at least F h  from the first surface, where F h >I d . 
 
     
     
       2. A plurality of pigment taggent flakes as defined in  claim 1 , wherein each flake is in the shape of a polygon, wherein the frame has at least two walls. 
     
     
       3. The plurality of pigment taggent flakes of  claim 1 , wherein the distances I d  and F h  are each greater than a thickness of a material forming the pigment taggent flake. 
     
     
       4. The plurality of pigment taggent flakes of  claim 1 , wherein a thickness of a material forming each pigment taggent flake is substantially uniform throughout the taggent flake. 
     
     
       5. The plurality of pigment taggent flakes of  claim 1 , wherein the frame comprises a structure extending substantially perpendicularly to the one or more walls and substantially parallel to the first surface. 
     
     
       6. A plurality of pigment taggent flakes as defined in  claim 2  wherein the indicia includes a symbol or logo, and wherein the walls each follow straight lines. 
     
     
       7. A plurality of pigment taggent flakes as defined in  claim 2  wherein each of the flakes has a same symbol or logo. 
     
     
       8. A plurality of pigment taggent flakes as defined in  claim 2  wherein F h /I d  is at least 1.5. 
     
     
       9. A plurality of pigment taggent flakes as defined in  claim 2  wherein each flake is encapsulated in a coating. 
     
     
       10. A plurality of pigment taggent flakes as defined in  claim 9  wherein the coating is selected from the group of metals, metal compounds, oxides, nitrates, polymers, and cermets. 
     
     
       11. A plurality of pigment taggent flakes as defined in  claim 2  wherein the indicia comprises one or more V-shaped grooves. 
     
     
       12. A plurality of pigment taggent flakes as defined in  claim 11  wherein the walls have a surface which extends substantially perpendicularly with respect to the first surface. 
     
     
       13. A plurality of pigment taggent flakes as defined in  claim 2  wherein the indicia can only be seen with magnification. 
     
     
       14. A plurality of pigment taggent flakes as defined in  claim 2  wherein each flake is comprised of a multilayer coating for providing a visible optical effect. 
     
     
       15. A plurality of pigment taggent flakes as defined in  claim 2 , wherein the flakes are coated with a non-conforming coating which lessens the depth of the grooves and wherein the indicia is not obscured by the coating. 
     
     
       16. A plurality of pigment taggent flakes as defined in  claim 15 , wherein the non-conforming coating enhances the contrast between the indicia and a background so that the indicia becomes more visible. 
     
     
       17. A plurality of pigment taggent flakes as defined in  claim 15  wherein the pigment taggent flakes are edible flakes. 
     
     
       18. A plurality of pigment taggent flakes, each flake comprising a first major surface having a frame about at least 2 sides thereof defined by walls extending upward or downward therefrom, and a region within the frame having a first flake surface, wherein the height of at least one of the frame walls is at least F h , and wherein the region within the frame of the first major surface has indicia defined by one or more grooves formed therein having a depth of less than I d , wherein F h >I d , wherein each flake has a thickness in a region absent the indicia and absent the frame that is less than F h , wherein the frame forms an outer periphery of the flake and at least partially surrounds the indicia and is separate therefrom. 
     
     
       19. A plurality of pigment taggent flakes as defined in  claim 18 , coated with a light transmissive non-conforming coating reducing the depth of grooves within the flake. 
     
     
       20. A plurality of pigment taggent flakes as defined in  claim 19  wherein the non-conforming coating effectively planarizes the flakes. 
     
     
       21. A plurality of pigment taggent flakes as defined in  claim 19 , wherein the non-conforming coating is a sol-gel coating. 
     
     
       22. A plurality of pigment taggent flakes as defined in  claim 19  wherein the pigment taggent flakes are edible flakes. 
     
     
       23. The plurality of pigment taggent flakes of  claim 18 , wherein the thickness of each pigment taggent flake is substantially uniform throughout the pigment taggent flake. 
     
     
       24. A plurality of taggent flakes, wherein each taggent flake has a periphery and wherein each taggent flake comprises:
 a material layer having a first surface on a first side thereof and a second surface on a second side thereof opposite the first side, wherein the material layer has a uniform thickness throughout the flake, 
 wherein each taggent flake has one or more grooves formed inside the periphery thereof to define an identifiable symbol, the one or more grooves having a maximum depth greater than the thickness of the taggent flake, and 
 wherein each taggent flake has a frame provided along at least a portion of the periphery thereof, the frame having a frame depth which is at least 50% greater than the maximum depth of the one or more grooves. 
 
     
     
       25. The plurality of taggent flakes of  claim 24 , wherein the plurality of taggent flakes includes a first taggent flake and a second taggent flake, wherein the frame is not provided along the entire periphery of the first taggent flake, and wherein the frame is provided along the entire periphery of the second taggent flake.